Apparatus for cleaning air and for humidifying air

ABSTRACT

A method for cleaning air utilizing an air cleaner which is smaller than conventional air cleaners, wherein a filter is formed on the peripheral portion of a disk and the filter is bent into a wave-shape such that irregularities of the wave are formed in the radial direction of the disk, so that air existing on the inside area of the disk is discharged to the outside of the disk through the filter.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/JP00/07615 which has an Internationalfiling date of Oct. 30, 2000, which designated the United States ofAmerica and was not published in English.

TECHNICAL FIELD

The present invention relates to a method for cleaning air and anapparatus therefor, and to a method for humidifying air and apparatustherefor.

BACKGROUND ART

Various conventional air cleaners utilizing fans and filters are known.The principle of these air cleaners is to make air pass through a filtercompulsively using a fan so as to make the dusts in the air be capturedby the filter, thereby cleaning the air. In most of the usual aircleaners, the fan and the filter are completely separated and wind madeby the fan is blown to the filter. Japanese Laid-open Patent Application(Kokai) No. 8-206436 discloses an air cleaner based on a sirocco fan ofwhich side wall is made of a filter so that air flow is made to passthrough the filter from the inside to the outside thereof by rotatingthe impeller, thereby cleaning the air.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a method for clearingair and an air cleaner using the same, by which the air cleaner can bemade more compact than the conventional air cleaners when theperformances are the same. Another object of the present invention is toprovide an air humidifier based on the similar principle to that of theair cleaner of the present invention, by which the air humidifier can bemade compact.

The present inventors intensively studied to discover that by bending afilter into wave-shape and by rotating the filter it self, the filterserves as both blades of an impeller and a filter, so that the aircleaner can be made more compact than the conventional air cleaners whenthe performances are the same.

That is, the present invention provides a method for cleaning aircomprising rotating a filter formed on peripheral portion of a disk suchthat the filter is formed along the peripheral portion of the disk so asto surround inside area of the disk, which filter is bent intowave-shape such that irregularities of the wave are formed in radialdirection of the disk, thereby discharging air existing on the insidearea of the disk to outside of the disk through the filter. The presentinvention also provides an air cleaner comprising a disk; a filterformed on peripheral portion of the disk such that the filter is formedalong the peripheral portion of the disk so as to surround inside areaof the disk, which filter is bent into wave-shape such thatirregularities of the wave are formed in radial direction of the disk;and means for rotating the disk. The present invention further providesa method for humidifying air comprising rotating a filter formed onperipheral portion of a disk such that the filter is formed along theperipheral portion of the disk so as to surround inside area of thedisk, which filter is bent into wave-shape such that irregularities ofthe wave are formed in radial direction of the disk, the filterretaining water therein, thereby discharging air existing on the insidearea of the disk to outside of the disk through the filter so as to givethe water retained in the filter to the air. The present invention stillfurther provides an air humidifier comprising a disk; a filter formed onperipheral portion of the disk such that the filter is formed along theperipheral portion of the disk so as to surround inside area of thedisk, which filter is bent into wave-shape such that irregularities ofthe wave are formed in radial direction of the disk, which filterretains water; and means for rotating the disk.

According to the present invention, an air cleaner having larger surfacearea of the filter per volume of the product (i.e., compact and havinghigh efficiency of collecting dusts) than the conventional air cleanersin which the fans and the filters are completely separated, and than theair cleaner disclosed in Japanese Laid-open Patent Application (Kokai)No. 8-206436 in which an impeller is enclosed in a filter, can beattained.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1 is an exploded perspective view of a preferred embodiment of theair cleaner according to the present invention.

FIG. 2 shows the air cleaner obtained by assembling the members shown inFIG. 1.

FIG. 3 is a partially cut away exploded view of an embodiment accordingto the present invention, in which a sealing plate is arranged in thegap between the upper end of the filter and the upper casing so as toreduce air flow passing through the gap.

FIG. 4 shows the air cleaner obtained by assembling the members shown inFIG. 3 (provided that the upper casing is removed).

FIG. 5 is a schematic cross-sectional view of the air cleaner shown inFIGS. 3 and 4.

FIG. 6 is a schematic cross-sectional view showing a preferredembodiment of the air cleaner according to the present invention, inwhich the air flow passing through the gap between the upper end of thefilter and the upper casing is reduced.

FIG. 7 is a schematic cross-sectional view showing another preferredembodiment of the air cleaner according to the present invention, inwhich the air flow passing through the gap between the upper end of thefilter and the upper casing is reduced.

FIG. 8 is a schematic cross-sectional view of a preferred embodiment ofthe air cleaner according to the present invention, in which a highelectric potential is given to the filter.

FIG. 9 is a schematic cross-sectional view of another preferredembodiment of the air cleaner according to the present invention, inwhich a high electric potential is given to the filter.

FIG. 10 is a schematic cross-sectional view of a preferred embodiment ofthe air cleaner according to the present invention, in which the filteris grounded and a high electric potential is given to the electrode.

FIG. 11 is a schematic cross-sectional view of another preferredembodiment of the air cleaner according to the present invention, inwhich the filter is grounded and a high electric potential is given tothe electrodes.

FIG. 12 is a schematic cross-sectional view of still another preferredembodiment of the air cleaner according to the present invention, inwhich the filter is grounded and a high electric potential is given tothe electrode.

FIG. 13 is a schematic cross-sectional view of still another preferredembodiment of the air cleaner according to the present invention, inwhich the filter is grounded and a high electric potential is given tothe electrode.

FIG. 14 is a schematic cross-sectional view of still another preferredembodiment of the air cleaner according to the present invention, inwhich the filter is grounded and a high electric potential is given tothe electrode.

FIG. 15 is a schematic cross-sectional view of a preferred embodiment ofthe air cleaner according to the present invention, with which thefilter can be back washed by blowing steam to the filter from theoutside of the filter.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of the present invention will now be describedreferring to FIGS. 1 and 2. FIG. 1 is an exploded perspective view of apreferred embodiment of the air cleaner or the air humidifier accordingto the present invention. FIG. 2 shows the air cleaner or air humidifierobtained by assembling the members shown in FIG. 1.

The air cleaner shown in FIGS. 1 and 2 comprises a disk 10 and a filter12 formed on and along the peripheral portion of the disk 10. As shown,the filter 12 surrounds an inside area of the disk 10, and the filter 12is bent into a wave-shape such that irregularities of the wave areformed in a radial direction of the disk 10. It should be noted thatalthough the irregularities of the filter are depicted in FIGS. 1 and 2in exact radiate form in the radial direction from a rotation shaft 13as the center thereof, each outer tip (the outer U-turning portion ofthe irregularities) is not necessarily in the center between theadjacent two inner tips (on the radiate lines), but may be shifted in aclockwise direction or anti-clockwise direction. That is, although theshape of the irregularities is depicted in FIGS. 1 and 2 in exactradiate form in the radial direction from the rotation shaft 14 as thecenter, the irregularities may be in the shape like a parabola or vanedirecting outward from the rotation shaft 14 as the center. The filter12 is fixed on the disk 10, so that by rotating the disk 10, the filter12 is also rotated together with the disk 10. On the center of the disk10, the rotation shaft 14 is fixed, and the rotation shaft 14 isconnected to a motor 16.

The above-described members are preferably contained in a casing. Acasing having a cylindrical shape or having a shape of a snail whereinonly one air inlet is formed (see FIGS. 3 and 4) may preferably beemployed. The casing shown in FIG. 1 comprises a lower casing 18 in theform of disk and an upper casing in the form of cylinder having a cover.The upper face of the upper casing 20 has air inlets 22 for inhaling airinto the area surrounded by the filter 12. The side face of the uppercasing 20 has air outlets 24 for discharging the air to the outside ofthe filter 12, which air comes through the filter 12. It should be notedthat the shapes and numbers of the air inlets 22 and of the air outlets24 are not restricted to those shown in the figures. In the embodimentshown in FIG. 1, since the upper casing 20 is fixed to the motor 16itself, the upper casing 20 does not rotate, and since the lower casing18 is fixed to the upper casing 20, the lower casing 18 also does notrotate.

As the filter 12, any filters conventionally employed in air cleanersmay be employed. Thus, the filter may be made of a relatively denseporous material by which the dusts and the like having diameters largerthan the diameters of the pores are removed, or may be made of a porousmaterial having a relatively large pore size and having adsorptionability, by which the dusts and the like having smaller sizes than thepores are also adsorbed to the filter. The filter may be provided withadsorption ability by retaining active carbon or the like. The materialof the filter is also not restricted at all and any optional porousmaterials made of paper, cloth, non-woven fabric, cotton, metal mesh,sponge, ceramics or the like may be employed.

In operation, the motor 16 is rotated so as to rotate the disk 10 andthe filter 12. The rotational speed is not restricted and mayappropriately be selected depending on the shape of the filter and thesize of the apparatus. Usually, the rotational speed may be about 200 to3000 rpm, preferably about 400 to 1000 rpm. Upon rotation of the filter12, since the filter 12 is bent into the wave-shape as shown in thefigures, the filter 12 serves as the blades of an impeller so that windis generated. As a result, the air existing on the inside area of thedisk 10, surrounded by the filter 12 is blown to the outside of the disk10 from the air outlets 24 formed on in the side face of the uppercasing 20 after passing through the filter 12, as indicated by arrows Bshown in FIG. 2. Simultaneously, as shown by arrows A in FIG. 2, air isinhaled from the air inlets 22 formed on the upper face of the uppercasing 20. Although air can pass through the filter 12, since therotational speed of the filter 12 is large, the filter 12 can serve asblades of an impeller because of the air resistance of the filter 12.Thus, the air existing on the inside area of the disk 10, which area issurrounded by the filter 12, is discharged to the outside after passingthrough the filter 12, wherein the air discharged to the outside iscleaned by passing through the filter 12.

In the above description, the case where the air cleaner is used in theposition in which the disk is held horizontally, was described. However,the above-described air cleaner can be used while holding the disk inthe vertical direction, that is, in the portrait orientation. Needlessto say, the air cleaner may also be used retaining the air cleaner at anoptional angle other than horizontal and vertical directions. This isalso true in the more preferred embodiments described below. In caseswhere the air cleaner is used in the portrait orientation in which thedisk is held vertically, although the terms such as “upper” casing and“lower casing” are not applicable, in the present specification, basedon the orientation where the disk is held horizontally and the disk islocated underside of the air cleaner, the terms “upper”, “lower”, “up”,“low”, “upper face”, “lower face” and the like may be used.

According to the present invention, an air cleaner having larger surfacearea of the filter per volume of the product (i.e., compact and havinghigh efficiency of collecting dusts) than the conventional air cleanersin which the fans and the filters are completely separated (hereinafterreferred to as “Prior Art 1” for convenience), and than the air cleanerdisclosed in Japanese Laid-open Patent Application (Kokai) No. 8-206436in which an impeller is enclosed in a filter (hereinafter referred to as“Prior Art 2” for convenience), can be attained.

For example, when the fan has an impeller having an outer diameter of110 mm, a thickness of 19 mm, a width of blade of 15 mm and the numberof blades of 25, and has a diameter of the air inlet of 84 mm, the areasof the filter in Prior Art 1, Prior Art 2 and the present invention willnow be compared. According to Prior Art 1, to make the apparatus mostcompact, the filter is arranged at the air inlet, so that the effectivefilter area is 5542 mm². On the other hand, according to Prior Art 2, itis 6566 mm². On the other hand, according to the present invention, whenthe wave number of the filter is the same as the number of blades of thePrior Art 1 and 2, the effective filter area is 16,150 mm² which is 2.9times that of Prior Art 1, and 2.5 times that of Prior Art 2. Thus, whenthe performances are the same, an air cleaner which can be made morecompact than the conventional air cleaners can be obtained. Therefore,the present invention is especially useful for the development of, forexample, portable air cleaners.

Preferred embodiments of the air cleaner according to the presentinvention described above will be further described.

With the air cleaner according to the present invention described above,a gap is formed between the edge of the filter, which edge is oppositeto the disk, and the casing, and air flows through the gap. That is, apart of the air inhaled from the air inlets 22 is discharged to theoutside of the air cleaner without passing through the filter, so thatthe efficiency is decreased accordingly. In preferred embodiments of thepresent invention, means for reducing air flow passing through the gap(hereinafter referred to as “air flow-reducing means” in the presentspecification) are provided. The term “reduce” herein means that theamount of the air passing through the above-mentioned gap is decreasedby providing the means when compared with the case where the means arenot provided. By providing the air flow-reducing means, the air-cleaningefficiency is further promoted.

A first embodiment of the air cleaner provided with such an airflow-reducing means will now be described referring to FIGS. 3 to 5.Although FIGS. 3 and 4 depicts the state wherein the disk 10 is heldvertically, as mentioned earlier, even in such a case, the casingcovering the side of the disk is called lower casing, and the casingcovering the side apart from the disk is called upper casing forconvenience.

In this embodiment, the motor 16 is fixed to the lower casing 18. In thelower casing 18, a snail-like partition wall 26 is formed. A part of thepartition wall 26 is opened to form an air outlet 24. Thus, in thisembodiment, the air outlets are gathered together to form a single airoutlet 24. The disk 10 and the filter 12 are contained inside of thepartition wall 26. In this embodiment, unlike the above-describedembodiment, the motor 16 is arranged on the lower casing 18. That is,the center portion of the disk 10 is protruded and the motor 16 isharbored in the space formed under the protrusion (see FIG. 5).

FIG. 3 is an exploded view. When the depicted members are assembled, themembers are arranged such that the positions penetrated by the alternatelong and short dash line are aligned on a single straight line. FIG. 4shows the assembled state (provided that the upper casing 20 is removedfor clarity). Among the openings depicted in the upper casing 20 in FIG.3, reference numeral 22 denotes an air inlet. Other openings are thosedepicted to show partially cut away portions for the purpose of easiercomprehension of the shape of the upper casing 20, so that they do notexist actually.

In this embodiment, an annular sealing plate covering the entire edge ofthe filter 12, which edge is opposite to the disk 10 is provided. Thesealing plate 28 rotates together with the filter 12. Therefore, thesealing plate 28 may be fixed to the edge by an adhesive or the like.Alternatively, the sealing plate 28 and the filter 12 or the disk 10 maybe connected by mechanical means such as hooks not shown. In FIG. 4, tobetter show the inner structure, the sealing plate 28 is shown in apartially cut away state.

FIG. 5 is a schematic sectional view of the air cleaner shown in FIGS. 3and 4. It should be noted that FIG. 5 shows the state wherein the disk10 is held horizontally (landscape orientation). As shown in FIG. 5,although the width W of the sealing plate 28 may preferably be about thesame as the width of the entire wavy structure of the filter 12, thewidth of the sealing plate 28 is not restricted thereto. By providingthe sealing plate 28, a part of the gap 30 between the upper edge of thefilter 12 and the upper casing 20 is closed so that the gap 30 is madesmaller. As a result, the air flow passing through the gap 30 isreduced. In addition, by providing the sealing plate 28, the gap 30 ismade to elongate in the horizontal direction in FIG. 5. That is,considering a single point on the upper edge of the filter 12, thedistance of the gap 30 in the horizontal direction (the horizontaldirection in FIG. 5) is nothing more than the thickness of the filter12. Since the thickness of the filter 12 is small, the distance of thenarrow gap is small accordingly, so that the air resistance is small andair flow is large. In contrast, when the sealing plate 28 is provided,the distance of the gap 30 in the horizontal direction is the width W ofthe sealing plate 28, shown in FIG. 5. Therefore, to pass through thisgap, the air must pass through the narrow gap spanning the entire widthW, so that the air resistance is large. Thus, the air flow is largelydecreased when compared with the case where the sealing plate 28 is notprovided.

FIG. 6 shows an embodiment which further improved the embodiment shownin FIGS. 3-5. In the embodiment shown in FIG. 6, a first annular ridge32 protruding opposite to the filter 12 is formed on the sealing plate28, and a second annular ridge 34 protruding to the sealing plate 28 isformed on the region of the upper casing 20, which region faces thesealing plate 28. Further, a third annular ridge 36 protruding to thesealing plate 28 is formed on the region of the upper casing 20, whichregion faces the sealing plate 28. The first ridge 32 is inserted intothe space formed between the adjacent second ridge 34 and the thirdridge 36. By forming these ridges, the amount of the air flowing throughthe gap 30 can be further decreased. The number of the ridge(s) formedon the sealing plate 28 or on the region of the upper casing 20, whichfaces the sealing plate 28, is not restricted to that shown in FIG. 6,and may be one or more, preferably about 1 to 6 ridges/10 mm length ofW.

In another embodiment shown in FIG. 7, the air flow-reducing means is inthe form of an annular elastic member 38. The upper end of the elasticmember 38 contacts the lower face of the upper casing 20, so that thegap 30 is completely closed. The elastic member 38 closing the gap 30may also be formed directly on the end of the filter 12 or on the uppercasing.

In another preferred mode of the present invention, the filter 12 iselectrically conductive, and the air cleaner further comprises means forgiving electric potential to the filter 12. The electrically conductivefilter 12 may be obtained by, for example, constituting the filter 12partly or entirely with particles or fibers of active carbon, carbon,copper, stainless steel, tin, nickel, zinc, titanium or the like; orapplying a well-known conductive coating containing a metal such as tin,nickel or zinc to the surface of the filter 12; or by immersing thefilter 12 in the electroconductive coating. By giving a high electricpotential to the filter 12, the dusts in the air can beelectrostatically adsorbed, so that the air-cleaning efficiency isfurther promoted. The electric potential given to the filter maypreferably be about 5 kV to 20 kV when the electric potential of theother parts of the apparatus is 0 V (i.e., the state of being grounded).The high electric potential may be given with a high voltage generator.The electric potential to be given may be positive or negative.

An embodiment in which a high electric potential is given to the filter12 will now be described based on FIG. 8. The apparatus shown in FIG. 8is similar to the apparatus shown in FIG. 6, but the upper casing 20 hasa two-stage structure as shown in FIG. 8, and a high voltage generator40 is harbored in the upper casing 20. The filter 12 is connected to thehigh voltage generator 40 through a high voltage line 42, a high voltagepin supporting plate 44, a high voltage pin 46, a high voltage pinholder 48, a terminal 50 and a high voltage line 52, and is insulated tothe parts other than these parts. A cylindrical wall 54 stands up fromthe disk 10 so as to surround the high voltage pin 46, therebypreventing dust from being attached to the high voltage region. A partof the high voltage pin 46 is harbored in the high voltage pin holder48. The high voltage pin 46 is slidable and is urged to the high voltagepin supporting plate 44 by a spring 56. The tip of the high voltage pin46 is pointed (round tip is also acceptable), and contacts the highvoltage pin supporting plate 44 above the rotation shaft of the motor.Thus, when a positive high voltage is generated by the high voltagegenerator 40, the filter 12 is an anode, and when a negative highvoltage is generated by the high voltage generator 40, the filter 12 isa cathode.

In the embodiment shown in FIG. 8, the high voltage pin 46 directlycontacts the high voltage pin supporting plate 44. However, the highvoltage pin 46 may contact the high voltage pin supporting plate 44 viaa conductive bearing.

The embodiment shown in FIG. 9 is also basically similar to theembodiment shown in FIG. 6, but the lower casing 18 has a two-stagestructure and the high voltage generator 40 is harbored in the lowercasing 18. The filter 12 is connected to the high voltage generator 40through a high voltage spring 58, a high voltage ring 60, a terminal 50and a high voltage line 52, and is insulated to the parts other thanthese parts. The high voltage spring 58 penetrates the disk 10 and isfixed thereto. One end of the high voltage spring 58 contacts the filter12 and the other end of the high voltage spring 58 slips on the highvoltage ring 60 with the rotation of the disk 10. The high voltage ring60 is annular, of which center is coincident with the rotation axis ofthe motor, and is made of a conductor such as a metal. Thus, when apositive high voltage is generated by the high voltage generator 40, thefilter 12 is an anode, and when a negative high voltage is generated bythe high voltage generator 40, the filter 12 is a cathode. Although thehigh voltage spring 58 shown in FIG. 9 is in the form of one line, itmay be in the form of a brush.

In another preferred embodiment of the present invention, the aircleaner further comprises an electrode, the filter is electricallyconductive, and the air cleaner further comprises means for applyingvoltage across the electrode and the filter. In this case, for example,the filter may be grounded and a high voltage may be applied to theelectrode. An appropriate voltage between the electrode and the filtermay be about 5 kV to 20 kV, although the voltage is not restricted tothis range. Although the position at which the electrode is arranged isnot restricted, it is preferred to arrange the electrode in the insidearea of the filter when the apparatus is viewed from the top. Byapplying a high voltage between the filter and the electrode, coronadischarge occurs between the filter and the electrode, so that theeffectiveness to collect the dusts is increased.

Various embodiments wherein the filter is grounded will now be describedbased on FIGS. 10 to 14.

In the embodiment shown in FIG. 10, the filter 12 is grounded through ahigh voltage line 42, the rotation shaft 14 of the motor and a motorcasing 16 b, and is insulated to the parts other than these parts. Thus,the electric potential of the filter 12 is 0 V. The tip of a highvoltage electrode 62 is pointed and positioned above the rotation shaft14 of the motor. The high voltage electrode 62 is connected to a highvoltage generator 40 through a terminal 50 and a high voltage line 52,and is insulated to the parts other than these parts. Thus, when apositive high voltage is generated by the high voltage generator 40, thefilter 12 is an anode, and when a negative high voltage is generated bythe high voltage generator 40, the filter 12 is a cathode.

The embodiment shown in FIG. 11 is similar to that shown in FIG. 10, buttwo high voltage electrodes 62 a and 62 b are formed. In thisembodiment, the high voltage electrodes 62 a and 62 b are arranged atpositions symmetrical to each other with respect to the rotation shaft14 of the motor. The number of the high voltage electrodes may be 3 ormore.

The embodiment shown in FIG. 12 is also almost the same as that shown inFIG. 10, but the shape of the high voltage electrode 62 is verticallyelongated shape hung from the upper side.

In the embodiment shown in FIG. 13, a cylindrical wall 64 of whichcenter is coincident with the rotation shaft 14 of the motor is formedon the upper casing 20. An annular high voltage electrode 62 is embeddedin the tip of the wall 64 and slightly protruded from the tip of thewall 64. The thin annular high voltage electrode 62 has a center whichis coincident with the center line of the rotation shaft 14 of themotor, and positioned at about the half of the thickness of the filter12 in the direction of the rotation axis of the filter 12. The highvoltage electrode 62 is connected to a high voltage generator 40 througha high voltage line 52.

In the embodiment shown in FIG. 14, a cylindrical high voltage electrode62 of which center is coincident with the center line of the rotationshaft 14 of the motor is formed on the disk 10. Although the surface ofthe cylindrical high voltage electrode 62 in the embodiment shown inFIG. 14 is smooth, the high voltage electrode 62 may have a number ofprojections. The high voltage electrode 62 is connected to a highvoltage generator 40 in the same manner as in the embodiment shown inFIG. 9. The cylindrical high voltage electrode 62 may not be formed onthe disk 10, but may be arranged in the upper casing 20 which has atwo-stage structure as in the embodiment shown in FIG. 13.

In the embodiments shown in FIGS. 10 to 14, the filter is groundedthrough the rotation shaft 14 of the motor and the motor casing 16 b.Since some bearings are not electrically conductive, however, the filtermay not be grounded in this manner. In such a case, it is necessary touse a member such as the high voltage pin 46 shown in FIG. 8. In FIG. 8,although the tip of the high voltage pin 46 does not contact therotation shaft 14 of the motor, if the high voltage pin supporting plate44 and the insulator are removed, the high voltage pin 46 contacts therotation shaft 14 of the motor. Thus, the filter may be grounded througha member like the high voltage pin 46.

Further, without using the end face of the rotation shaft 14 of themotor, the filter may be grounded through a metal brush arranged in themotor 16, which connects the rotation shaft and the motor casing 16 b.

In the embodiments shown in FIGS. 10 to 14, the filter 12 is grounded.However, in the structure such as shown in FIG. 8 or 9, the high voltageelectrode(s) 62 is(are) arranged as in the embodiments shown in FIGS. 10to 14, and a high electric potential having a polarity opposite to thatof the high voltage electrode(s) 62 may be applied to the filter 12,thereby applying a voltage across the filter 12 and the high voltageelectrode(s) 62.

Such an air cleaner was prepared and the increase in the air-cleaningefficiency by applying electric voltage was examined. That is, the aircleaner had the basic structure of the embodiment shown in FIG. 10. Asthe filter, 0.4 m² of active carbon paper was used. The diameter of thedisk 10 was 250 mm, the gap 30 between the disk 10 and the upper casing20 was 7 mm, the difference between the inner diameter and the outerdiameter of the filter 12 was 67 mm, and the number of turns of the waveof the filter was 60. The rotational speed of the disk 10 was 1000 rpm.A voltage of +8.76 kV was applied to the filter 12, and a voltage of−8.76 kV was applied to the high voltage electrode 62 at the air inlet.The discharge current was 110 μA. A chamber having a volume of 35.2 m³was filled with smoke, and the rates of decrease in the concentration ofthe dusts were compared when the high voltage was applied and notapplied.

The rate of decrease in the concentration of the dusts when the highvoltage was applied was about 5 times that when the high voltage was notapplied.

When using the above-mentioned air cleaner according to the presentinvention, the filter comes to be clogged with time and the air-cleaningefficiency decreases. In such a case, by replacing the filter with newone, the air-cleaning efficiency can be restored to the original state.

Alternatively, a structure with which the filter can be back washed maybe employed. By back washing the filter to regenerate the filter, theair-cleaning efficiency may be restored to the original state. Further,by adjusting the amount of steam and the rotational speed of the disk,sterilization of the filter may also be attained, so that the apparatuscan be kept clean. Further, in cases where the filter 12 contains activecarbon, the active carbon is also regenerated so that its deodorizingability is restored. The back wash may preferably be carried out byblowing steam to the filter from the outside thereof. Thus, an aircleaner with which the filter can be back washed has means for blowingsteam to the filter from the outside thereof. Such an air cleaner maypreferably have a tank receiving the water generated by condensation ofthe steam, and a passage guiding the water to the tank. Further, sincethe back wash is preferably carried out at a rotational speed of thefilter smaller than the rotational speed during the air cleaningoperation, the air cleaner preferably has means for decreasing therotational speed of the filter to, for example, about 0.1 to 30 rpm.

An embodiment with which the filter can be back washed is shown in FIG.15. The air cleaner of the embodiment shown in FIG. 15 is operated whilevertically holding the disk 10 at least when the filter is back washed.The embodiment shown in FIG. 15 has a steamer 66 and a steam duct 68 asmeans for blowing steam to the filter 12 from the outside of the filter12. The embodiment further comprises a tank 70 for receiving the watergenerated by condensation of the steam and a passage 72 which guides thegenerated water to the tank 70.

It should be noted that the above-described air cleaner may be used notonly as it is, but also as a part of a vacuum cleaner or the like bybeing arranged, for example, at the air outlet of the vacuum cleaner orthe like.

In the foregoing description, air cleaners were described. By making thefilter 12 retain water, the above-described air cleaners function ashumidifiers. Such a humidifier may easily be attained by continuouslyblowing water shower to the filter 12 from a water duct not shown. Byusing such a filter, since the air absorbs moisture when the air passesthrough the filter 12, cleaning of the air and humidification of the aircan simultaneously be attained.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. An air cleaner comprising: a disk; a filterformed on a peripheral portion of said disk, said filter being formedalong the peripheral portion of said disk so as to surround an insidearea of said disk, said filter being bent into a wave-shape such thatirregularities of the wave are formed in a radial direction of saiddisk, and said filter being electrically conductive; at least oneelectrode; means for applying electric voltage across said at least oneelectrode and said filter; and means for rotating said disk, whereinsaid at least one electrode is arranged in an inside area of said filterwhen said cleaner is viewed from a direction opposite to said disk, andcorona discharge continuously occurs between said at least one electrodeand said filter.
 2. The air cleaner according to claim 1, wherein saidfilter is grounded.
 3. The air cleaner according to claim 1, wherein anelectric potential with a polarity opposite to that of said at least oneelectrode is given to said filter.
 4. The air cleaner according to claim1, further comprising a casing enclosing said disk and said filter, saidcasing having at least one air inlet through which air to be cleaned isinhaled into the space surrounded by said filter, said casing having atleast one air outlet formed on the portion of said casing that surroundssaid filter, air discharged through said filter being discharged to theoutside of said casing through said at least one air outlet.
 5. The aircleaner according to claim 4, further comprising means for reducing airflow through a gap between an edge of said filter opposite to said diskand said casing, said means for reducing air flow being formed on saidedge of said filter, and said edge is opposite to said disk.
 6. The aircleaner according to claim 5, wherein said means for reducing air flowis an annular sealing plate which covers the entire said edge, saidannular sealing plate is formed on said edge of said filter.
 7. The aircleaner according to claim 6, wherein at least one annular ridgeprotruding to the direction opposite to said filter is formed on saidsealing plate, and at least one annular ridge protruding to thedirection of said sealing plate is formed on the region of said casing,and said region faces said sealing plate.
 8. The air cleaner accordingto claim 7, wherein a plurality of said ridges are formed on at leastone of said region of said casing facing said sealing plate, and a tipportion of an opposing ridge is inserted into the space between adjacenttwo ridges of said plurality of ridges.
 9. The air cleaner according toclaim 5, wherein said means for reducing air flow is an annular elasticmember which closes said gap, said elastic member being formed on saidedge of said filter or on said casing.
 10. The air cleaner according toclaim 6, wherein said means for reducing air flow is an annular elasticmember which closes said gap, said elastic member being formed on saidedge of said filter or on said sealing plate, or on said casing.
 11. Anair-humidifier which is the air cleaner according to claim 1, whereinsaid filter retains water.